Semiconductor device, switching power supply device, composite power supply device, and linear ic

Abstract

Provided is a semiconductor device including a common terminal connected to an external capacitor outside of the semiconductor device, a function selection unit configured to execute a selection operation for outputting a selection signal for selecting a designated function according to an amount of charge accumulated in the external capacitor, and an internal power supply unit configured to supply a voltage to an internal circuit provided inside the semiconductor device, in which the external capacitor is electrically connected to the function selection unit when the selection operation is performed, and the external capacitor is electrically connected to the internal power supply unit and the internal circuit when a supply operation for supplying a supply voltage from the internal power supply unit to the internal circuit is performed.

What is claimed is: 
     
         1 . A semiconductor device comprising:
 a common terminal connected to an external capacitor outside of the semiconductor device;   a function selection unit configured to execute a selection operation for outputting a selection signal for selecting a designated function according to an amount of charge accumulated in the external capacitor; and   an internal power supply unit configured to supply a voltage to an internal circuit provided inside the semiconductor device, wherein   the external capacitor is electrically connected to the function selection unit when the selection operation is performed, and the external capacitor is electrically connected to the internal power supply unit and the internal circuit when a supply operation for supplying a supply voltage from the internal power supply unit to the internal circuit is performed.   
     
     
         2 . The semiconductor device according to  claim 1 , wherein
 the function selection unit charges the external capacitor for a predetermined amount of time in the selection operation.   
     
     
         3 . The semiconductor device according to  claim 1 , wherein
 the supply operation is performed after the selection operation is performed.   
     
     
         4 . The semiconductor device according to  claim 1 , wherein
 a discharge operation for discharging the external capacitor is executed before the selection operation is performed.   
     
     
         5 . The semiconductor device according to  claim 1 , wherein
 the function selection unit holds the selection signal and continues outputting the selection signal after the selection operation has ended.   
     
     
         6 . The semiconductor device according to  claim 1 , wherein
 the function selection unit has
 a reference voltage output unit configured to output reference voltages that are different voltages, and 
 a comparing unit configured to compare a selection voltage that corresponds to the charge accumulated in the external capacitor with the respective reference voltages, and output a result of the comparison. 
   
     
     
         7 . The semiconductor device according to  claim 6 , wherein
 the reference voltage output unit has
 a standard voltage source configured to output a given standard voltage, and 
 a voltage divider configured to divide the standard voltage and supply a plurality of the reference voltages that are different voltages, and 
   the comparing unit has a plurality of comparators configured to compare the selection voltage with the respective reference voltages and output a result of the comparison.   
     
     
         8 . The semiconductor device according to  claim 6 , wherein
 the reference voltage output unit supplies the reference voltages that are different voltages to the comparing unit.   
     
     
         9 . The semiconductor device according to  claim 1 , further comprising:
 a common wire connected to the common terminal;   an internal circuit connection wire connected to the internal circuit;   a first switch disposed between the common wire and the function selection unit;   a second switch disposed between the common wire and the internal power supply unit;   a third switch disposed between the common wire and the internal circuit connection wire; and   a control unit, wherein   the control unit performs control to bring the first switch into a conductive state and bring the second switch and the third switch into a non-conductive state when the selection operation is performed, and bring the first switch into a non-conductive state and bring the second switch and the third switch into a conductive state when the supply operation is performed.   
     
     
         10 . A switching power supply device comprising:
 the semiconductor device according to  claim 1 ; and   a switching output stage configured to be driven by the semiconductor device.   
     
     
         11 . A composite power supply device comprising:
 the semiconductor device according to  claim 1 ; and   a plurality of output stages configured to be driven by the semiconductor device, wherein   at least one of the plurality of output stages is operated by the semiconductor device.   
     
     
         12 . A linear integrated circuit that uses the semiconductor device according to  claim 1 .